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Deferred writeback.

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This commit is contained in:
Steven Robertson
2011-11-11 17:37:27 -05:00
parent 05e1d08681
commit eb43b151dc
4 changed files with 360 additions and 206 deletions
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439
cuburn/code/iter.py
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@ -122,7 +122,6 @@ class IterCode(HunkOCode):
bodies = [self._xfbody(i,x) for i,x in sorted(info.genome.xforms.items())]
bodies.append(iterbody)
self.defs = '\n'.join(bodies)
self.decls += self.pix_helpers.substitute(info=info)
decls = """
// Note: for normalized lookups, uchar4 actually returns floats
@ -132,78 +131,6 @@ __device__ int rb_head, rb_tail, rb_size;
"""
pix_helpers = Template("""
__device__
void read_pix(float4 &pix, float &den) {
den = pix.w;
{{if info.pal_has_alpha}}
read_half(pix.z, pix.w, pix.z, den);
{{endif}}
}
__device__
void write_pix(float4 &pix, float den) {
{{if info.pal_has_alpha}}
write_half(pix.z, pix.z, pix.w, den);
{{endif}}
pix.w = den;
}
__device__
void update_pix(uint64_t ptr, uint32_t i, float4 c) {
{{if info.pal_has_alpha}}
asm volatile ({{crep('''
{
.reg .u16 sz, sw;
.reg .u64 base, off;
.reg .f32 x, y, z, w, den, rc, tz, tw;
// TODO: this limits the accumulation buffer to <4GB
shl.b32 %0, %0, 4;
cvt.u64.u32 off, %0;
add.u64 base, %1, off;
ld.cg.v4.f32 {x, y, z, den}, [base];
add.f32 x, x, %2;
add.f32 y, y, %3;
mov.b32 {sz, sw}, z;
cvt.rn.f32.u16 tz, sz;
cvt.rn.f32.u16 tw, sw;
mul.f32 tz, tz, den;
mul.f32 tw, tz, den;
fma.f32 tz, %4, 65535.0, tz;
fma.f32 tw, %5, 65535.0, tw;
add.f32 den, 1.0;
rcp.approx.f32 rc, den;
mul.f32 tz, tz, rc;
mul.f32 tw, tw, rc;
cvt.rni.u16.f32 sz, tz;
cvt.rni.u16.f32 sw, tw;
mov.b32 z, {sz, sw};
st.cs.v4.f32 [base], {x, y, z, den};
}
''')}} : "+r"(i) : "l"(ptr), "f"(c.x), "f"(c.y), "f"(c.z), "f"(c.w));
{{else}}
asm volatile ({{crep('''
{
.reg .u64 base, off;
.reg .f32 x, y, z, den;
// TODO: this limits the accumulation buffer to <4GB
shl.b32 %0, %0, 4;
cvt.u64.u32 off, %0;
add.u64 base, %1, off;
ld.cg.v4.f32 {x, y, z, den}, [base];
add.f32 x, x, %2;
add.f32 y, y, %3;
add.f32 z, z, %4;
add.f32 den, den, 1.0;
st.cs.v4.f32 [base], {x, y, z, den};
}
''')}} : "+r"(i) : "l"(ptr), "f"(c.x), "f"(c.y), "f"(c.z));
{{endif}}
}
""")
def _xfbody(self, xfid, xform):
px = self.pcp.xforms[xfid]
tmpl = Template(r"""
@ -249,19 +176,23 @@ __global__ void reset_rb(int size) {
}
__global__
void iter(uint64_t accbuf_ptr, mwc_st *msts, float4 *points,
const iter_params *all_params, int nsamps_to_generate) {
void iter(
uint64_t out_ptr,
mwc_st *msts,
float4 *points,
const iter_params *all_params,
int nsamps_to_generate
) {
const iter_params *global_params = &(all_params[blockIdx.x]);
__shared__ int nsamps;
nsamps = nsamps_to_generate;
{{if info.acc_mode != 'deferred'}}
__shared__ float time_frac;
time_frac = blockIdx.x / (float) gridDim.x;
{{endif}}
// load params to shared memory cooperatively
for (int i = threadIdx.y * blockDim.x + threadIdx.x;
i * 4 < sizeof(iter_params); i += blockDim.x * blockDim.y)
i < (sizeof(iter_params) / 4); i += blockDim.x * blockDim.y)
reinterpret_cast<float*>(&params)[i] =
reinterpret_cast<const float*>(global_params)[i];
@ -272,9 +203,10 @@ void iter(uint64_t accbuf_ptr, mwc_st *msts, float4 *points,
__syncthreads();
int this_rb_idx = rb_idx + threadIdx.x + 32 * threadIdx.y;
mwc_st rctx = msts[this_rb_idx];
// TODO: 4th channel unused. Kill or use for something helpful
float4 old_point = points[this_rb_idx];
float x = old_point.x, y = old_point.y,
color = old_point.z, fuse_rounds = old_point.w;
float x = old_point.x, y = old_point.y, color = old_point.z;
{{if info.chaos_used}}
int last_xf_used = 0;
@ -290,116 +222,139 @@ void iter(uint64_t accbuf_ptr, mwc_st *msts, float4 *points,
__syncthreads();
{{endif}}
bool fuse = false;
while (1) {
// This condition checks for large numbers, Infs, and NaNs.
if (!(-(fabsf(x) + fabsf(y) > -1.0e6f))) {
x = mwc_next_11(rctx);
y = mwc_next_11(rctx);
color = mwc_next_01(rctx);
fuse_rounds = {{info.fuse / 32}};
}
// This condition checks for large numbers, Infs, and NaNs.
if (!(-(fabsf(x) + fabsf(y)) > -1.0e6f)) {
x = mwc_next_11(rctx);
y = mwc_next_11(rctx);
color = mwc_next_01(rctx);
fuse = true;
}
// 32 rounds is somewhat arbitrary, but it has a pleasing 32-ness
for (int i = 0; i < 32; i++) {
// TODO: link up with FUSE, etc
for (int round = 0; round < 256; round++) {
{{if info.chaos_used}}
{{precalc_chaos(pcp, std_xforms)}}
{{precalc_chaos(pcp, std_xforms)}}
// For now, we don't attempt to use the swap buffer when chaos is used
float xfsel = mwc_next_01(rctx);
// For now, we don't attempt to use the swap buffer when chaos is used
float xfsel = mwc_next_01(rctx);
{{for prior_xform_idx, prior_xform_name in enumerate(std_xforms)}}
if (last_xf_used == {{prior_xform_idx}}) {
{{for xform_idx, xform_name in enumerate(std_xforms[:-1])}}
if (xfsel <= {{pcp['chaos_'+prior_xform_name+'_'+xform_name]}}) {
apply_xf_{{xform_name}}(x, y, color, rctx);
last_xf_used = {{xform_idx}};
} else
{{endfor}}
{
apply_xf_{{std_xforms[-1]}}(x, y, color, rctx);
last_xf_used = {{len(std_xforms)-1}};
}
{{for prior_xform_idx, prior_xform_name in enumerate(std_xforms)}}
if (last_xf_used == {{prior_xform_idx}}) {
{{for xform_idx, xform_name in enumerate(std_xforms[:-1])}}
if (xfsel <= {{pcp['chaos_'+prior_xform_name+'_'+xform_name]}}) {
apply_xf_{{xform_name}}(x, y, color, rctx);
last_xf_used = {{xform_idx}};
} else
{{endfor}}
{
printf("Something went *very* wrong.\n");
asm("trap;");
}
{{else}}
{{precalc_densities(pcp, std_xforms)}}
float xfsel = cosel[threadIdx.y];
{{for xform_name in std_xforms[:-1]}}
if (xfsel <= {{pcp['den_'+xform_name]}}) {
apply_xf_{{xform_name}}(x, y, color, rctx);
} else
{{endfor}}
apply_xf_{{std_xforms[-1]}}(x, y, color, rctx);
int sw = (threadIdx.y * 32 + threadIdx.x * 33) & {{NTHREADS-1}};
int sr = threadIdx.y * 32 + threadIdx.x;
swap[sw] = fuse_rounds;
swap[sw+{{NTHREADS}}] = x;
swap[sw+{{2*NTHREADS}}] = y;
swap[sw+{{3*NTHREADS}}] = color;
__syncthreads();
// We select the next xforms here, since we've just synced.
if (threadIdx.y == 0 && threadIdx.x < {{NWARPS}})
cosel[threadIdx.x] = mwc_next_01(rctx);
fuse_rounds = swap[sr];
x = swap[sr+{{NTHREADS}}];
y = swap[sr+{{2*NTHREADS}}];
color = swap[sr+{{3*NTHREADS}}];
{{endif}}
if (fuse_rounds > 0.0f) continue;
{{if 'final' in cp.xforms}}
float fx = x, fy = y, fcolor = color;
apply_xf_final(fx, fy, fcolor, rctx);
{{endif}}
float cx, cy, cc;
{{precalc_camera(info, pcp.camera)}}
{{if 'final' in cp.xforms}}
{{apply_affine('fx', 'fy', 'cx', 'cy', pcp.camera)}}
cc = fcolor;
{{else}}
{{apply_affine('x', 'y', 'cx', 'cy', pcp.camera)}}
cc = color;
{{endif}}
uint32_t ix = trunca(cx), iy = trunca(cy);
if (ix >= {{info.acc_width}} || iy >= {{info.acc_height}})
continue;
uint32_t i = iy * {{info.acc_stride}} + ix;
float4 outcol = tex2D(palTex, cc, time_frac);
update_pix(accbuf_ptr, i, outcol);
last_xf_used = {{len(std_xforms)-1}};
}
} else
{{endfor}}
{
printf("Something went *very* wrong.\n");
asm("trap;");
}
int num_okay = __popc(__ballot(fuse_rounds == 0.0f));
// Some xforms give so many badvals that a thread is almost guaranteed
// to hit another badval before the fuse is over, causing the card to
// spin forever. To avoid this, we count a fuse round as 1/4 of a
// sample below.
if (threadIdx.x == 0) atomicSub(&nsamps, 256 + num_okay * 24);
fuse_rounds = fmaxf(0.0f, fuse_rounds - 1.0f);
{{else}}
{{precalc_densities(pcp, std_xforms)}}
float xfsel = cosel[threadIdx.y];
{{for xform_name in std_xforms[:-1]}}
if (xfsel <= {{pcp['den_'+xform_name]}}) {
apply_xf_{{xform_name}}(x, y, color, rctx);
} else
{{endfor}}
apply_xf_{{std_xforms[-1]}}(x, y, color, rctx);
int sw = (threadIdx.y * 32 + threadIdx.x * 33) & {{NTHREADS-1}};
int sr = threadIdx.y * 32 + threadIdx.x;
swap[sw] = fuse ? 1.0f : 0.0f;
swap[sw+{{NTHREADS}}] = x;
swap[sw+{{2*NTHREADS}}] = y;
swap[sw+{{3*NTHREADS}}] = color;
__syncthreads();
if (nsamps <= 0) break;
// We select the next xforms here, since we've just synced.
if (threadIdx.y == 0 && threadIdx.x < {{NWARPS}})
cosel[threadIdx.x] = mwc_next_01(rctx);
fuse = swap[sr];
x = swap[sr+{{NTHREADS}}];
y = swap[sr+{{2*NTHREADS}}];
color = swap[sr+{{3*NTHREADS}}];
{{endif}}
{{if info.acc_mode == 'deferred'}}
int tid = threadIdx.y * 32 + threadIdx.x;
int offset = 4 * (256 * (256 * blockIdx.x + round) + tid);
int *log = reinterpret_cast<int*>(out_ptr + offset);
{{endif}}
if (fuse) {
{{if info.acc_mode == 'deferred'}}
*log = 0xffffffff;
{{endif}}
continue;
}
{{if 'final' in cp.xforms}}
float fx = x, fy = y, fcolor = color;
apply_xf_final(fx, fy, fcolor, rctx);
{{endif}}
float cx, cy, cc;
{{precalc_camera(info, pcp.camera)}}
{{if 'final' in cp.xforms}}
{{apply_affine('fx', 'fy', 'cx', 'cy', pcp.camera)}}
cc = fcolor;
{{else}}
{{apply_affine('x', 'y', 'cx', 'cy', pcp.camera)}}
cc = color;
{{endif}}
uint32_t ix = trunca(cx), iy = trunca(cy);
if (ix >= {{info.acc_width}} || iy >= {{info.acc_height}}) {
{{if info.acc_mode == 'deferred'}}
*log = 0xffffffff;
{{endif}}
continue;
}
uint32_t i = iy * {{info.acc_stride}} + ix;
{{if info.acc_mode == 'atomic'}}
float4 outcol = tex2D(palTex, cc, time_frac);
float *accbuf_f = reinterpret_cast<float*>(out_ptr + (16*i));
atomicAdd(accbuf_f, outcol.x);
atomicAdd(accbuf_f+1, outcol.y);
atomicAdd(accbuf_f+2, outcol.z);
atomicAdd(accbuf_f+3, 1.0f);
{{elif info.acc_mode == 'global'}}
float4 outcol = tex2D(palTex, cc, time_frac);
float4 *accbuf = reinterpret_cast<float4*>(out_ptr + (16*i));
float4 pix = *accbuf;
pix.x += outcol.x;
pix.y += outcol.y;
pix.z += outcol.z;
pix.w += 1.0f;
*accbuf = pix;
{{elif info.acc_mode == 'deferred'}}
// 'color' gets the top 9 bits. TODO: add dithering via precalc.
uint32_t icolor = cc * 512.0f;
asm("bfi.b32 %0, %1, %0, 23, 9;" : "+r"(i) : "r"(icolor));
*log = i;
{{endif}}
}
if (threadIdx.x == 0 && threadIdx.y == 0)
@ -407,10 +362,140 @@ void iter(uint64_t accbuf_ptr, mwc_st *msts, float4 *points,
__syncthreads();
this_rb_idx = rb_idx + threadIdx.x + 32 * threadIdx.y;
points[this_rb_idx] = make_float4(x, y, color, fuse_rounds);
points[this_rb_idx] = make_float4(x, y, color, 0.0f);
msts[this_rb_idx] = rctx;
return;
}
// Block size, shared accumulation bits, shared accumulation width.
#define BS 1024
#define SHAB 12
#define SHAW (1<<SHAB)
// These two accumulators, used in write_shmem, hold {density, red} and
// {green, blue} values as packed u16 pairs. The fixed size represents 4,096
// pixels in the accumulator.
__shared__ uint32_t s_acc_dr[SHAW];
__shared__ uint32_t s_acc_gb[SHAW];
// Read from the shm accumulators and write to the global ones.
__device__
void write_shmem_helper(
float4 *acc,
const int glo_base,
const int idx
) {
float4 pix = acc[glo_base+idx];
uint32_t dr = s_acc_dr[idx];
pix.x += (dr & 0xffff) / 255.0f;
pix.w += dr >> 16;
uint32_t gb = s_acc_gb[idx];
pix.y += (gb & 0xffff) / 255.0f;
pix.z += (gb >> 16) / 255.0f;
acc[glo_base+idx] = pix;
}
// Read the point log, accumulate in shared memory, and write the results.
// This kernel is to be launched with one block for every 4,096 addresses to
// be processed, and will handle those addresses.
//
// log_bounds is an array mapping radix values to the first index in the log
// with that radix position. For performance reasons in other parts of the
// code, the radix may actually include bits within the lower SHAB part of the
// address, or it might not cover the first few bits after the SHAB part;
// log_bounds_shift covers that. glob_addr_bits specifies the number of bits
// above SHAB which are address bits.
__global__ void
__launch_bounds__(BS, 1)
write_shmem(
float4 *acc,
const uint32_t *log,
const uint32_t *log_bounds,
const int log_bounds_shift
) {
const int tid = threadIdx.x;
const int bid = blockIdx.x;
// TODO: doesn't respect SHAW/BS
// TODO: compare generated code with unrolled for-loop
s_acc_dr[tid] = 0;
s_acc_gb[tid] = 0;
s_acc_dr[tid+BS] = 0;
s_acc_gb[tid+BS] = 0;
s_acc_dr[tid+2*BS] = 0;
s_acc_gb[tid+2*BS] = 0;
s_acc_dr[tid+3*BS] = 0;
s_acc_gb[tid+3*BS] = 0;
__syncthreads();
// TODO: share across threads - discernable performance impact?
int lb_idx_lo, lb_idx_hi;
if (log_bounds_shift > 0) {
lb_idx_hi = ((bid + 1) << log_bounds_shift) - 1;
lb_idx_lo = (bid << log_bounds_shift) - 1;
} else {
lb_idx_hi = bid >> (-log_bounds_shift);
lb_idx_lo = lb_idx_hi - 1;
}
int idx_lo, idx_hi;
if (lb_idx_lo < 0) idx_lo = 0;
else idx_lo = log_bounds[lb_idx_lo] & ~(BS-1);
idx_hi = (log_bounds[lb_idx_hi] & ~(BS - 1)) + BS;
float rnrounds = 1.0f / (idx_hi - idx_lo);
float time = tid * rnrounds;
float time_step = BS * rnrounds;
int glo_base = bid << SHAB;
for (int i = idx_lo + tid; i < idx_hi; i += BS) {
int entry = log[i];
// TODO: constant '11' is really just 32 - 9 - SHAB, where 9 is the
// number of bits assigned to color. This ignores opacity.
bfe_decl(glob_addr, entry, SHAB, 11);
if (glob_addr != bid) continue;
bfe_decl(shr_addr, entry, 0, SHAB);
bfe_decl(color, entry, 23, 9);
float colorf = color / 512.0f;
float4 outcol = tex2D(palTex, colorf, time);
// TODO: change texture sampler to return shorts and avoid this
uint32_t r = 255.0f * outcol.x;
uint32_t g = 255.0f * outcol.y;
uint32_t b = 255.0f * outcol.z;
uint32_t dr = atomicAdd(s_acc_dr + shr_addr, r + 0x10000);
uint32_t gb = atomicAdd(s_acc_gb + shr_addr, g + (b << 16));
uint32_t d = dr >> 16;
// Neat trick: if overflow is about to happen, write the accumulator,
// and subtract the last known values from the accumulator again.
// Even if the ints end up wrapping around once before the subtraction
// can occur, the results after the subtraction will be correct.
// (Wrapping twice will mess up the intermediate write, but is pretty
// unlikely.)
if (d == 250) {
atomicSub(s_acc_dr + shr_addr, dr);
atomicSub(s_acc_gb + shr_addr, gb);
write_shmem_helper(acc, glo_base, shr_addr);
}
time += time_step;
}
__syncthreads();
int idx = tid;
for (int i = 0; i < (SHAW / BS); i++) {
write_shmem_helper(acc, glo_base, idx);
idx += BS;
}
}
''')
return tmpl.substitute(
info = self.info,

7
cuburn/code/util.py
View File

@ -71,6 +71,13 @@ float3 hsv2rgb(float3 hsv);
#define M_SQRT2 1.41421353816986f
#define M_SQRT1_2 0.70710676908493f
#define bfe(d, s, o, w) \
asm("bfe.u32 %0, %1, %2, %3;" : "=r"(d) : "r"(s), "r"(o), "r"(w))
#define bfe_decl(d, s, o, w) \
int d; \
bfe(d, s, o, w)
// TODO: use launch parameter preconfig to eliminate unnecessary parts
__device__
uint32_t gtid() {